If they are just torn at the foot and/or crotch and you have long enough pieces undamaged from the legs, you can make excellent arm warmers or fingerless gloves out of them. I love these because they fill in the gap that can occur between gloves and sleeves and keep the cold air out. I also wear them when reading in bed because my sleeves fall down my arms and my exposed arms get cold.

My style sensibilities can tend toward scruffy/punky, but sometimes I layer the torn tights if I like them and if the tears slow. (Also I ride a bike to get around and have found I almost always get crotch tears after a few wears. Boo.Also, you can cut them in strips and use them to hold tomato plants to their stakes. Or use them in place of rubber bands.